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Topic: Maximum Energy & Entropies  (Read 2516 times)

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Offline baggravation

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Maximum Energy & Entropies
« on: April 15, 2009, 03:56:30 AM »
I have a question about maximum energy and maximum entropy.

How would you know whether the tendency towards maximum energy favours to reactants or the products.

Secondly, how would you know whether the tendency towards maximum entropy favours the reactants or products? 


Example:
CO (g) + 1/2 02 <-> CO2                  delta H = -282.5 KJ

Offline megnsc

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Re: Maximum Energy & Entropies
« Reply #1 on: April 17, 2009, 10:17:12 AM »
Since you are taking 1.5 moles of gas and making 1 mole of gas, the entropy of the system has decreased: there are fewer ways of ordering the gas molecules.  We expect then that DS is negative, this sort of favors the reactants. 

Since DH is also negative, that would mean that the products have less energy than the reactants, so the enthalpy term would favor the products. 

Overall, this reaction would be spontaneous at low values of T.  The spontaneity (or free energy) of the reaction is based on DG = DH - TDS.  If DG < 0, we say the reaction will occur.

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